The present plastic core composite construction has general application wherever outside exposure to the elements or inadvertent impact blows are present or possible which, singly or in combination, are apt to crack, split, spall, or otherwise rupture a plastic core or body and especially a metallic layer on the core. The composite construction accordingly can be used as a mirror shell or housing, wheel covers, bumpers and the like for automotive vehicles, snow mobiles, snow-throwers, and other like vehicles. For purposes of illustration, the invention is described particularly in connection with a mirror shell or housing.
At present a mirror shell and the like is manufactured by die casting a metal such as zinc, for example. The casting is then finished by metal plating a decorative finish on an outer side of the casting and is then fitted with a mirror structure within the casting shell. In an endeavor to reduce the manufacturing costs and the weight of many parts and attachments for vehicles, it has been proposed to replace the more expensive and heavier metal of the mirror shell with lighter weight plastic. It has been estimated that a savings of about 1.5 pounds per outside, rear view mirror is obtainable for a total weight savings of three pounds or more per vehicle for just rear view mirrors.
Unfortunately, when plastic cores are plated with metal to cover the plastic and provide a decorative, pleasing appearance, the properties of the resulting product, especially as to impact resistance, are considerably worsened. The impact resistance of the plastic core alone can be better than the impact resistance of a metal-coated plastic core. Yet, it is important to make the appearance of the plastic core attractive and still preserve the integrity of the metallic layer for customer satisfaction. Nevertheless, the impact resistance of metal-plated plastic can be so lowered by the metal layer as to cause the plastic composite to fail specifications. This has been found to be true regardless of the plastic used for the core or similar substrate.